September 11 has been George Bush's rhetorical trumpcard since he climbed the rubble of the World Trade Centre and rallied rescue workers through a megaphone nearly four years ago.

Many believe that was his finest hour and he attempted to invoke the same spirit in his speech on Tuesday night.

With five mentions of September 11 in his 30-minute address, Mr Bush attempted to weld the Iraq insurgency to the battle with al-Qaida in the public's mind, where the two have been drifting apart.

He spoke of the shared "totalitarian ideology" of the Iraqi insurgents and Osama bin Laden's organisation.

The best way to take these enemies on was "to defeat them abroad before they attack us at home", he said.

This time, Mr Bush said, the US would not "wait to be attacked".

Failure in Iraq would leave that country a haven for terrorism and a launching pad for attacks on the homeland, just as Afghanistan had been.

Finally, the insurgents were trying "to shake our will in Iraq, just as they tried to shake our will on September 11 2001".

Critics were quick to point out that several of those links were more a consequence of the Iraq invasion than a justification for it.

The connections described by Mr Bush at Fort Bragg were more conceptual than the close relationship described by the White House before the war.

The prewar rhetoric portrayed that relationship as long and deep. Dick Cheney, the vice-president, who took the lead in making the claims described evidence of the relationship as "overwhelming".

Mr Cheney said in late 2001 it had been "pretty well confirmed" that the lead September 11 hijacker Mohamed Atta had met an Iraqi intelligence officer in Prague in April 2000.

Mr Bush said in October 2002: "We've learned that Iraq has trained al-Qaida members in bomb-making and poisons and gases."

He also pointed to the alleged presence of Abu Musab al-Zarqawi, a Jordanian Islamist militant in Baghdad, and of a radical Sunni group, Ansar al-Islam, in Kurdistan as further proof of the connection.

Those alleged connections crumbled under postwar scrutiny.

Investigations by the Senate's intelligence committee and by the September 11 commission of inquiry found no evidence of an operational alliance between al-Qaida and Saddam Hussein. There did seem to have been contacts in Sudan and Afghanistan in the 1990s but they did not lead to a "collaborative relationship", the commission found.

The al-Qaida detainee who claimed Iraqis had given the group chemical and biological weapons training retracted his testimony, and Zarqawi's links with Bin Laden appeared to have been loose before the war but much firmer as a consequence of it.

In an intercepted message to al-Qaida leaders in January 2003, Zarqawi offered to "swear fealty" to Bin Laden in return for support for his group in Iraq, suggesting that no such bond existed between them before the invasion.

Washington's attempts to link Saddam with al-Qaida and September 11 have been a source of strife between Britain and America since before the war.

London did not say so publicly at the time but senior MI6 officials were furious at the prewar attempts to make the connection.

British intelligence officials warned ministers that an invasion of Iraq would increase the threat posed by al-Qaida sympathisers, an outcome that was reflected in the president's speech on Tuesday.

Despite the dearth of evidence of a solid link since the war, the picture of the relationship remains muddy in the US.

Mr Cheney, in particular, has refused to retract his war claims and has continued to hint at hidden connections between Saddam and Bin Laden.

Robin Hayes, a Republican congressman from North Carolina, appeared on television yesterday claiming to have seen secret evidence of Iraqi involvement in the September 11 attacks which he could not share.

Such cryptic claims were widely rejected as groundless yesterday, but Mr Bush's more subtle rendering of the alleged Iraq-Bin Laden axis will serve to blur the hard lines between fact and propaganda.

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